Estuaries in the Gulf of America (Gulf) are experiencing increased temperatures, flood-producing storms, and more extreme weather events. As the climate continues to change, it’s important for fisheries managers to understand how environmental conditions influence localized fish and invertebrate populations. Fisheries-independent monitoring data provide valuable insight into juvenile recruitment dynamics, enabling examination of these patterns relative to changing habitat conditions. 

The Mississippi Sound is an estuary complex naturally influenced by six tributaries, but freshwater diversion poses a considerable threat. Periodic openings of the Bonnet Carré Spillway cause rapid freshwater influxes, altering salinity and exerting significant impacts on resident species. In recent years, the frequency and duration of Spillway openings have increased, with events in 2011 and 2019 resulting in federally declared fisheries disasters.

My objectives were to evaluate relationships between hydrological variability and juvenile recruitment of eight ecologically and economically important species: brown shrimp (Farfantepenaeus aztecus), white shrimp (Litopenaeus setiferus), blue crab (Callinectes spp.), Atlantic Croaker (Micropogonias undulatus), Sand Seatrout (Cynoscion arenarius), Spotted Seatrout (Cynoscion nebulosus), Spot (Leiostomus xanthurus), and Gulf Menhaden (Brevoortia patronus). A 15-year (2009–2023) fishery-independent trawl survey dataset analyzed using generalized additive models with negative binomial error structures assessed the influence of temperature, salinity, river discharge, and Spillway discharge on juvenile abundance. All species exhibited shifts in peak recruitment associated with hydrological variability and Spillway influence, though the direction and magnitude of effects varied. 

Species recruiting in late winter (e.g., Spot and Gulf Menhaden) responded positively to temperature, while others showed negative or no discernable trends. Roughly half the species exhibited clear salinity preferences, whereas the remainder showed no discernable trends. Brown shrimp juvenile abundance declined with increasing river discharge, while most other species responded positively (Sand Seatrout not significant). Species exhibiting positive responses to river discharge also responded favorably to moderate Spillway flows, however extreme or prolonged Spillway openings led to substantial declines.  Species that showed negative responses to river discharge (e.g., brown shrimp and Sand Seatrout) exhibited consistent declines across Spillway flow levels. My results indicated that river discharge and Spillway releases impacted recruitment trends across taxa, which should be considered in species-specific management.